Stress‐ and pathway‐specific impacts of impaired jasmonoyl‐isoleucine (JA‐Ile) catabolism on defense signalling and biotic stress resistance

作者：Valentin Marquis, Ekaterina Smirnova, Laure Poirier, Julie Zumsteg, Fabian Schweizer, Philippe Reymond, Thierry Heitz · 发表于：Plant Cell & Environment · 年份：2020 · DOI：10.1111/pce.13753 · 被引用次数：51 · 研究领域：Insect-Plant Interactions and Control、Insect and Pesticide Research、Plant Parasitism and Resistance

Jasmonate synthesis and signalling are essential for plant defense upregulation upon herbivore or microbial attacks. Stress-induced accumulation of jasmonoyl-isoleucine (JA-Ile), the bioactive hormonal form triggering transcriptional changes, is dynamic and transient because of the existence of potent removal mechanisms. Two JA-Ile turnover pathways operate in Arabidopsis, consisting in cytochrome P450 (CYP94)-mediated oxidation and deconjugation by the amidohydrolases IAR3/ILL6. Understanding their impacts was previously blurred by gene redundancy and compensation mechanisms. Here we address the consequences of blocking these pathways on jasmonate homeostasis and defenses in double-2ah, triple-3cyp mutants, and a quintuple-5ko line deficient in all known JA-Ile-degrading activities. These lines reacted differently to either mechanical wounding/insect attack or fungal infection. Both pathways contributed additively to JA-Ile removal upon wounding, but their impairement had opposite impacts on insect larvae feeding. By contrast, only the ah pathway was essential for JA-Ile turnover upon infection by Botrytis, yet only 3cyp was more fungus-resistant. Despite building-up extreme JA-Ile levels, 5ko displayed near-wild-type resistance in both bioassays. Molecular analysis indicated that restrained JA-Ile catabolism resulted in enhanced defense/resistance only when genes encoding negative regulators were not simultaneously overstimulated. This occurred in discrete stress- and pathw...